The present invention relates to the fabrication of composite panels and mouldings, and more particularly to the fabrication of panels and mouldings formed by a combination of selected dissimilar materials.
The use of mouldings and other linear millwork such as base (floorboard skirting), flat and split door jambs, crown (ceiling surrounds), rabbeted jambs (frames), brick mould, and casings (door and window surrounds), is well known. Mouldings generally provide architectural detail and are decorative. Some mouldings also support light loads, such as door jambs on which door hinges are mounted. It is important that the exposed wood used in the mouldings be of a quality compatible with the desired finish, and with any load supported. For example, if mouldings are to be left in a natural or varnished state, the wood usually should be clear and bright, free of knots, fungus stains, pitch, wood discolorations, other visible blemishes and glued joints. Such mouldings are known in the construction industry as "solid clear grade lineal mouldings," or simply "solid clear mouldings."
Mouldings intended to be painted (or otherwise covered to hide glue joints, color, grain or defects in the wood) are known as "paint grade mouldings." Paint grade mouldings are used in most applications. The ability to use a lower grade knotty, defective, discolored, or otherwise imperfect wood in the fabrication of paint grade mouldings is important, considering that higher quality clear and bright grade woods are generally less plentiful and more expensive. The finger joint manufacturing process involved in the fabrication of paint grade mouldings removes defects that are not hidden by paint in finished mouldings. In recent years, the use of clear solid grade mouldings has declined, while the use of paint grade mouldings has become more common.
Finger joint moulding is produced using a fifty year old process. It is a complex multi-step process that includes: 1) ripping strips from a thick plank of wood; 2) cross cutting blocks of paintable and finger-jointable defect-free segments out of each strip by removing those segments having knots, splits, blemishes, or other defects; 3) reripping the cut blocks strips where required to a narrower width to remove any broken or wane edges; 4) finger jointing by machining and glueing the resulting accumulated clear blocks to form finger joint blanks of the desired length and dimension; 5) if necessary, resawing with a band saw or rip saw the finger joint blanks in a desired dimension or beveled shape; 6) passing the resulting blank through a multi-headed profiled knife moulder in lineal fashion to form mouldings in their final contoured cross-sectional shape; and 7) precision trimming and dado processing the moulding into the final desired length. Typical remaining steps for finger joint moulding processing, before shipping, may include sanding or patching, priming or painting, and packaging.
Though finger joint moulding is a widely accepted and used paint grade moulding, there are several undesirable characteristics associated with this manufacturing technique. First, the production of finger joint mouldings is slow, labor intensive, and generates a lot of wood waste. Even with skilled craftsmen and modem machines, approximately 45 to 50 percent of the original wood volume used is lost during the many processing stages (as sawdust, shavings, and defect blocks). The entire board footage volume of finished finger joint moulding profiles fabricated requires an equivalent volume of high quality clear solid wood after processing. The lumber materials used in the fabrication of finger joint moulding are expensive and of limited availability. If the process exposes a defect previously hidden inside the wood and it becomes apparent that a section or block is defective in that manner after it is fabricated into a blank, the entire blank may be deemed defective and subject to complete remanufacture.
Each discrete section of wood or blank used in finger joint moulding is composed of multiple smaller blocks or discrete wood sections. Therefore, each wood section is susceptible to its own natural characteristic tendencies of warping, splitting, bowing, cupping, twisting, and other such problems. Wood moulding that warps, cracks, or otherwise distorts is difficult and frustrating to work with, and increases scrap.
Another undesirable characteristic of prior art finger joint mouldings, shared with other paint grade mouldings and varnish grade mouldings, is that each moulding piece usually has to be fabricated separately. Rarely are more than two pieces machined simultaneously in one moulding machine, and two pieces may be machined simultaneously only when the profile has a very small cross-sectional dimension as most moulders are not wider than eight inches, twelve inches at the most. Machining one piece at a time is costly in both machine time and labor. Such processing adds significantly to the expense of the moulding and usually results in smaller mouldings being only slightly less costly than mouldings having larger cross sections, or solid clear grade lineal mouldings formed from higher quality wood. Since each moulding piece is moulded separately and since cross cutting is a separate operation, each piece also has to be handled, measured and cross cut by itself.
Other mouldings are formed as substrates that have veneers covering some or all of their surfaces. Veneers are common in mouldings used in furniture component construction. In prior art veneer mouldings, an inexpensive substrate of wood, or other material such as medium density fiberboard, is machined or formed in a quality fashion to the desired shape of the final moulding. A thin strip of separate veneer material (usually cut or sliced from a high quality wood) is then bent or contoured in a shape that conforms to the surface of the substrate. The veneer is adhered to the exposed surfaces of the substrate. If made correctly, veneer mouldings can have an attractive appearance resembling, but being less costly than solid clear wood mouldings. Veneer moulding is, however, more expensive than finger joint paint grade moulding. The use of veneer mouldings is usually reserved for low volumes of high quality, expensive hardwood species of which solid wood is too costly or difficult to obtain.
The prior art veneer mouldings have important shortcomings. To form a thin veneer into certain standard commercial profiles of desired angles or shapes, the veneer has to be bent sharply to conform to the contours of the profile. Most veneers are formed from a wood that cannot adapt to very sharp bending, and attempting to bend too sharply causes cracking. Although most cracking occurs in manufacturing, such cracking may occur after the moulding leaves the factory, perhaps during installation of the moulding. Sharp angles are, therefore, not usually found on veneered mouldings. In addition, the adhesive used to attach the veneer to the substrate may fail, allowing the veneer to peel away. Furthermore, veneer mouldings are expensive, requiring a careful machining of the substrate in a linear fashion before the application of the veneer, which is also accomplished in a linear fashion. The costs associated with acquiring veneers and is attaching them are relatively high. Veneer mouldings often have a better appearance than solid or finger joint wood, but are nevertheless often equated with either lower valued case good products or furniture, cabinets, and picture frames.
The machinery that is necessary and used to produce mouldings is an important consideration. Moulding machines that are commonly used to shape contoured lineal surfaces of mouldings are rarely capable of producing a moulding or process a blank that is as much as one foot or more in width. These machines are relied upon largely because they can provide cuts having extremely close tolerances and/or complex curves. If mouldings are milled by machines that cannot operate within these tolerances, certain edges of the work piece may be misshaped, the exposed wood of the mouldings may have raised or torn grains, or the lineal surfaces may have washboard effects. Further machining, or occasional sanding, is necessary to smooth the surfaces of work pieces having such washboard effects. Many times it is impossible to repair the surface and the entire product must be scrapped. Other prior art machines do not produce mouldings that are as attractive as mouldings made on moulding machines. These machines also require complex engineering and tooling. They are individually built by hand and require precise tolerances in the machine and tool steel used. They are, therefore, relatively expensive to purchase. Operating these moulding machines requires a high degree of skill and maintenance is expensive and technically burdensome.
Another type of machine used in the conventional fabrication of mouldings is the planer or matcher. These machines are used primarily to plane or smooth the outer surface of lumber or a blank in a lineal manner. It is generally impossible to cut through a piece of wood to form multiple separate lineal mouldings from a single piece of wood using a planer. Although planers are less expensive to buy and operate than moulders that have similar board footage throughput capabilities, they can perform only a limited function.
Rip saws are also used in moulding fabrication to make cuts that extend lineally through pieces of wood. Rip saw cuts do not necessarily generate much wood waste. However, forming curved or contoured lineal surfaces using rip saws is generally not possible, because rip saws do not control the width, depth and straightness of a cut to the degree necessary.
It should thus be evident that moulders, planers, and rip saws each have their own purposes in moulding fabrication. Each piece of prior art machinery works on very few pieces at any one time in a lineal fashion. Additionally, to form many mouldings, there are multiple necessary processing steps that often require different machines.
In certain prior art processes, where work pieces that have edge-glued panels or laminated substrate panels machined into a panel or moulding having finished contoured edges or surfaces, the product is produced by machining, using routers as cutting tools which move about the work piece while maintaining the work piece in a fixed location and position. An example of a machine that cuts in this manner is a computerized numerical control routing machine. Such routers are usually limited to a maximum of four or five routing heads that work simultaneously on one work piece. Moreover, computerized numerical control systems are complex to program, expensive to purchase, and typically machine large surface areas relatively slowly. In general, they are not a practical alternative to moulding machines.
The greatest volume of mouldings sold is of standardized profile shapes and sizes that have simple but well defined contoured cross-sections. These mouldings with rectangular profiles, rounded edges, simple "S" faces, ogee faces or edges, and radius curved cross-sections represent approximately 85 percent of all mouldings sold. Intricately curved and angled mouldings and very complex profiles traditionally represent approximately only about 15 percent of moulding volume. Many prior art machines used to produce mouldings are, therefore, more complex, and can provide profiles of much more intricate architectural detail and variations in design than is necessary for the predominant volume of mouldings made and consumed by the housing, furniture and commercial construction industries.
Reducing the costs of machinery, labor, and the bulk of the raw material consumed in moulding production, and yet providing a technique for producing mouldings formed from multiple wood sections with a high quality appearance, is most desirable. Limiting the percentage of high quality wood contained within such mouldings, and the waste associated with producing such mouldings, is also highly desirable. Replacing such high quality woods with lower quality woods, wood substitutes, or other materials is desirable where such replacement does not detract from the appearance sought or the properties necessary for use of the mouldings. Production of a veneered moulding that appears as if it were solid wood and permits the machining of sharp cross sectional curves and angles on the contoured profile is also desirable. It is desirable to provide a fabrication process that is not extremely complex to carry out and is of lower cost than using a conventional moulder, which can inexpensively mill the wood into high quality mouldings with close cross sectional tolerances and do so in volume. It is further desirable to provide a moulding fabrication process that is not more labor intensive than has customarily been necessary. The present invention can satisfy these desires, using relatively uncomplicated technology.